Electric machines, such as motors and generators, typically include a stator that is mounted inside a housing and a rotor that is supported for rotation relative to the stator. There are several conventional methods for placing the winding wire on the stator teeth of non-segmented electric machines. A transfer winding method involves initially winding the wire and then transferring the pre-wound wire onto the stator teeth. Transfer winding tends to leave excess winding wire or loops around axial ends of the stator teeth. Transfer winding can typically utilize approximately 60-65% of available stator slot area.
When multiple phases of the electric machine are interconnected using transfer winding, the winding wire for teeth associated with one polarity of one phase are typically wound using a continuous wire and then transferred onto the corresponding stator teeth. As a result, the cost of separately connecting the phase wires to the winding wire can be avoided.
A needle winding method employs a needle that winds the wire directly on the stator teeth. The needle, however, takes up some of the stator slot area, which reduces slot fill to approximately 50% for non-segmented stators. When multiple phases of the electric machine are interconnected using needle winding, the winding wire for teeth associated with one polarity of one phase are also typically wound using a continuous wire to eliminate the cost of connecting the phase wires to the winding wires.
To improve slot fill and other characteristics of the electric machine, some manufacturers have split the stator into multiple stator segment assemblies. Each stator segment assembly typically includes one stator tooth. The individual stator segment assemblies of segmented stator electric machines are usually wound individually. For example, the stator segment assemblies of some brushless permanent magnet electric machines include an end cap assembly that is attached to a segmented stator core. Winding wire is wound around the end cap assembly and the stator core. Some switched reluctance electric machines also include a segmented stator.
Opposite ends of the winding wire for each stator segment assembly are typically wound around terminals that are integrated with the end cap assembly. When using segmented stators, the stator segment assemblies are manually interconnected to form first, second and third phases of the electric machine. This approach has relatively high labor cost.
Other approaches include using printed circuit boards (PCB) or lead frames to connect the terminals or IDCs. Both PCBs and IDCs have a relatively high cost. PCBs also have limited heat dissipation, which may pose a problem for low voltage electric machines with higher current levels. Lead frames require a substantial amount of space and require a multiple step manufacturing process such as stamping or molding.